One of the struggles of my life

Pray for them, respect their beliefs. As someone who also has an athiest brother, you cant force them to believe, they have to choose whether or not to accept Christ.

I pray for god to strengthen their faith in his word every night for a while. I guess I shouldn't force my believes. They used to believe, but they quit believing because apparently there's "not enough proof that God's real" which in Hebrews 11:1 says that faith is the substance of things hoped for and the evidence of things not seen. Also Proverbs says to trust in the Lord with all your heart, and lean not on your own understanding. I guess I should just let them choose to believe because I've tried countless times to convince them that God's real. I guess I just have to accept their fate... Unless they start believing again.

Its tough to know the truth and know that you may never see them again. Pray for your 2 brothers that claim atheism day and night. I would feel secure, depending on the "level" of autism your other brother experiences, on his getting into heaven. I recently watched a video by a young woman, raised in a Jewish household, that gave her life to Jesus and prayed tirelessly for her family to join with her. Her mother and brother are now followers of Jesus as well. Don't give up on them.